64 A DESKJET FRUIT. 



end or at the summits of the lobes ; and it needs but a 

 slight intensihcation of this pointed tendency to produce 

 forthwith the sharp defensive foliage of gorse, thistles^ 

 and holly. Often one can see all the intermediate stages 

 still surviving under one's very eyes. The thistles, them- 

 selves, for example, vary from soft and unarmed species 

 which haunt out-of-the-way spots beyond the reach of 

 browsing herbivores, to such trebly-mailed types as that 

 enemy of the agricidtural interest, the creeping thistle, 

 in which the leaves continue themselves as prickly wings 

 down every side of the steni, so that the whole plant is 

 amply clad from head to foot in a defensive coat of fierce 

 and bristling spearheads. There is a connnon little Eng- 

 lish meadow weed, the rest-harrow, which in rich and 

 uncropped fields produces no defensive armour of any 

 sort ; but on the much-browsed-over suburban commons 

 and in similar exposed spots, where only gorse and black- 

 thorn stand a chance for their lives against the cows and 

 donkeys, it has developed a protected variety in which 

 some of the branches grow abortive, and end abruptly in 

 stout spines like a hawthorn's. Only those rest-harrows 

 have there survived in the sharp struggle for existence 

 which happened most to batiie their relentless pursuers. 

 Desert plants naturally carry this tendency to its 

 highest point of development. Nowhere else is the 

 struggle for life so fierce ; nowhere else is the enemy so 

 goaded by hunger and thirst to desperate measures. It 

 is a place for internicine warfare Hence, all desert 

 plants are quite absurdly prickly. The starving herbivores 

 will attack and devour under such circumstances even 

 thorny weeds, which tear or sting their tender tongues 



